The invention relates to an apparatus for guiding a curved strip consisting of a stiff material.
An apparatus for guiding a curved strip of a stiff material, as disclosed for example in U.S. Pat. No. 3,243,132, comprises a cylindrical drum having a peripheral surface which forms a contact surface against which at least a portion of the strip lies in such a way that, in that portion, the strip is of a curved configuration about a transverse axis, with the transverse curvature of the strip being resiliently removed. When the strip is wound around the peripheral surface of the cylindrical drum in a plurality of layers, the peripheral surface of the drum forms the contact surface for the innermost layer or turn of the wound strip, while the contact surface for each of the outer layers or turns of strip is formed by the outward surface of the respective next inward layer or turn of the strip. So that the strip which is of a curved or cambered configuration, being therefore resiliently prestressed in such a way that it is curved about its longitudinal axis, can be wound on to and unwound from the drum in a fairly well-defined manner, disposed upstream of the peripheral surface of the drum is an arrangement of clamping and guide rollers which are pressed against the wide sides of the strip and which ensure that, as the strip is wound on to or off the drum, the strip cannot tilt about its longitudinal axis or bulge outwardly, if the part of the strip which is not wound on the drum is subjected to a compression loading in the longitudinal direction of the strip towards the drum.
However, that construction does not make it possible to provide for a precisely defined, that is to say slip-free, conversion of the rotary movement of the drum into a linear movement of the strip end which is the `free end`, that is to say, the end which is not secured to the drum, or vice-versa. In addition, the clamping and guide rollers give rise to frictional losses which cause problems in many situations of practical use.